A life

There are more than one hundred definitions of the concept of “life”, and many of them contradict each other. Life can be defined through such words as “system”, “substance”, “complexity (of information)”, “(self-) reproduction”, “evolution”, etc. A minimum definition consistent with 123 definitions: life is self-reproduction with changes ( Eng. Life is self-reproduction with variations ) ^[7] .

Friedrich Engels gave the following definition: “Life is a way of existence of protein bodies, the essential point of which is a constant metabolism with their external nature , and with the cessation of this metabolism, life also stops, which leads to protein decomposition” ^[8] .

Life can be defined as active, ongoing with the expenditure of energy received from outside, maintenance and self-reproduction of the molecular structure ^[8] .

The Russian scientist MV Volkenstein gave a new definition to the concept of life: “Living bodies existing on Earth are open, self-regulating and self-reproducing systems built from biopolymers - proteins and nucleic acids” ^[9] .

According to the views of one of the founders of thanatology M. Bish , life is a combination of phenomena that resist death .

From the point of view of the second law of thermodynamics , life is a process or system, the vector of development of which is opposite in direction to other, inanimate objects of the universe, and is aimed at reducing its own entropy (see Thermal death ).

VN Parmon gave the following definition: “Life is a phase-segregated form of existence of functioning autocatalysts capable of chemical mutations and having undergone a rather long evolution due to natural selection ” ^[10] .

According to Ozanger and Morowitz : “Life is a property of matter, leading to the conjugate circulation of bioelements in the aquatic environment, driven, ultimately, by the energy of solar radiation along the path of increasing complexity.”

There are also cybernetic definitions of life. According to A. A. Lyapunov’s definition, life is “a highly stable state of matter that uses information encoded by the states of individual molecules to generate conservation reactions”.

There is also a physiological definition of life, given in 1929 by A. F. Samoilov , which was not thoroughly studied by a great scientist: “Life is a vicious circle of reflex activity.” The gap in this circle in any place (“coma” state) means a sharp limitation of the parameters of life or even the absence of life. Now you can expand this concept somewhat and indicate the reasons on which this vicious circle depends. Namely: the state of the external environment, the "will power" of the individual, the internal vegetative principles of the body, not subject to the "will power" .

According to the official definition of NASA , developed in 1994 and used in the tasks of finding life in the Universe, life is “a self-sustaining chemical system capable of Darwinian evolution” ^[11] .

Life in the Universe - this term should be understood as a complex of problems and tasks aimed at finding life. In the most general case, life is interpreted as broadly as possible - as an active form of the existence of matter , in a sense higher than its physical and chemical forms of existence. Thus, in the general statement of the problem there is no requirement that life be similar to earthly, and there are a number of theories that prove that life can take other forms. However, the main approach used in astrobiology in constructing search strategies consists of two stages ^[12] :

1. The study of the origin of life on Earth. Development of key points. The skeleton is ^[13] :
   • Data on the geological life of the planet, in particular volcanism, tectonics and magnetic field.
   • Climate history data and our understanding of the mechanisms that govern it.
   • Basic ideas about the structure of life, in particular about DNA, cells and the boundaries of the survival of living organisms
   • Data on the origin of living organisms and their evolution.
2. Alignment of basic principles with astronomical observations and theories and purposeful search. Includes:
   • Search for viable exoplanets
   • The construction of theories of formations, which include complex molecular formations, from which life could subsequently originate.
   • Study of the Solar System and correlation of the obtained data with data on extrasolar systems

Also, a search for extraterrestrial civilizations can be singled out in a separate area of ​​research. There are three main issues in this area:

• What to search?
• How to search?
• Where to looking for?

And here, in constructing a research strategy, an extremely important, if not key, role belongs to the Drake equation , in addition to the types of civilizations according to Kardashev . ^[fourteen]

Life is qualitatively superior to other forms of the existence of matter with respect to the variety and complexity of chemical components and the dynamics of transformations occurring in living. Living systems are characterized by a much higher level of structural and functional ordering in space and time.

Living systems exchange energy , matter and information with the environment, thus being open systems . At the same time, unlike inanimate systems, they do not equalize energy differences and rearrange structures in the direction of more likely forms, but continuously work “against equilibrium”. This is the basis for erroneous claims that living systems supposedly do not obey the second law of thermodynamics . However, a decrease in entropy in living systems is possible only by increasing entropy in the environment ( negentropy ), so that in general the process of increasing entropy continues, which is in full agreement with the requirements of the second law of thermodynamics.

At different times regarding the origin of life on Earth, the following hypotheses were put forward:

• Creation Hypothesis (see Creationism )
• Spontaneous hypothesis
• The stationary state hypothesis
• The hypothesis of biochemical evolution
• Panspermia Hypothesis

The hypotheses of spontaneous generation and stationary state are of only historical or philosophical interest, since the results of scientific studies refute them.

The panspermia hypothesis does not solve the fundamental question of the origin of life, it only puts it off to the even more distant past of the Universe, although it cannot be excluded as a hypothesis about the beginning of life on Earth .

Thus, the only universally recognized in science at present is the hypothesis of biochemical evolution .

An organism is a living body with a combination of properties that distinguish it from inanimate matter. The body is the basic unit of life, the real carrier of its properties, since only in the cells of the body do the processes of life take place. As a separate individual, the body is part of the species and population , being a structural unit of the population-species standard of living.

Organisms are one of the main subjects of study in biology . For convenience, all organisms are distributed into different groups and categories, which makes up the biological system for their classification . Their most common division is nuclear and non-nuclear . By the number of cells that make up the body, they are divided into non-systematic categories of unicellular and multicellular . A special place between them is occupied by single-celled colonies .

The formation of an integral multicellular organism is a process consisting of the differentiation of structures (cells, tissues , organs ) and functions and their integration both in ontogenesis and in phylogenesis . Many organisms are organized into intraspecific communities (for example, the family or the work team in humans).

The world of living creatures has several million species . All this variety of organisms is studied by biological systematics , the main task of which is to build a system of the organic world. Wildlife is now usually divided into eight kingdoms : viruses , protists , archaea , chromists , bacteria , fungi , plants and animals .

Wildlife is organized into ecosystems that make up the biosphere .

A living system is a unity consisting of self-organizing , self-reproducing elements that actively interact with the environment, having specific characteristics inherent in living things.

In science, there is an opinion that a system consisting of living people, such as economic or social, has a number of qualities that make it similar to a living organism. This is a living creature with its own cells, metabolism and nervous system. In it, various public institutions play the role of organs, each of which performs its special function in maintaining the vital functions of the body. For example, the army acts similarly to the immune system, protecting the body from intrusions from the outside, while the government works like a brain, making decisions and managing. This idea was first voiced back in antiquity by the Greek philosopher Aristotle .

In its development, science has moved away from the mechanistic view of organisms. In the study of living systems, scientists are attracted by the variety of processes by which the system adapts to a constantly changing external environment. Many ideas and methods, united in the field of “theory of complexity”, led to the awareness of organisms as self-organizing adaptive systems. The processes in such systems are decentralized, indefinite and constantly changing. The complex adaptive behavior of such systems arises in the process of interaction between individual autonomous components. Models in which control is subordinated to a separate block were considered insufficiently true for most real systems.

Metabolism (metabolism) is a set of chemical reactions that occur in a living organism to maintain life. These processes allow organisms to grow and multiply, maintain their structures and respond to environmental influences.

Metabolism is usually divided into two stages: catabolism and anabolism . During catabolism, complex organic substances degrade to simpler ones, usually releasing energy. And in the processes of anabolism - from more simple ones more complex substances are synthesized and this is accompanied by energy costs.

All living organisms have the property of reproducing their own kind, which ensures the continuity and continuity of life. Different methods of reproduction are divided into two main types: asexual and sexual . For organisms with a cellular structure, the basis of all forms of reproduction is cell division.

Behavior - the ability of animals to change their actions under the influence of internal and external factors ^[15] , a characteristic feature of the animal type of organization ^[16] . Behavior is of great adaptive importance, allowing animals to avoid negative environmental factors ^[17] . In multicellular organisms, behavior is controlled by the nervous system .

Plants and bacteria also have the ability to actively, moreover, orderly movement under the influence of external factors (taxis). An example is the photo- and chemotaxis of bacteria, blue-green algae ^[18] . Higher plants are also not devoid of the ability to move. Plant nictinastias are well known - opening and closing flowers in connection with a change of day and night, leaf phototropisms, plant movements when hunting animals , hydro- and chemotropisms of roots ^{[approx. 1] [19]} .

Nevertheless, since the mechanisms of plant movement are purely physiological in nature, one cannot talk about the presence of either behavior or psyche. In psychology, plant movements are referred to the pre-mental level of reflection.

Behavior, unlike the psyche , is available for direct observation and is the subject of a wide range of sciences , from psychology , ethology , zoopsychology and comparative psychology to behavioral ecology .

Biology is the science of life ( living nature ), one of the natural sciences , the objects of study of which are living things and their interaction with the environment . Biology studies all aspects of life, in particular, the structure, functioning, growth, origin, evolution and distribution of living organisms on Earth . Classifies and describes living things, the origin of their species , the interaction between themselves and with the environment .

Как особая наука биология выделилась из естественных наук в XIX веке , когда учёные обнаружили, что живые организмы обладают некоторыми общими для всех характеристиками. Термин «биология» был введён независимо несколькими авторами: Фридрихом Бурдахом в 1800 году, в 1802 году Готфридом Рейнхольдом Тревиранусом ^[20] и Жаном Батистом Ламарком .

В основе современной биологии лежат пять фундаментальных принципов: клеточная теория , эволюция , генетика , гомеостаз и энергия ^{[21] [22]} . В наше время биология — стандартный предмет в средних и высших учебных заведениях всего мира. Ежегодно публикуется более миллиона статей и книг по биологии, медицине и биомедицине ^[23] .

В биологии выделяют следующие уровни организации:

• Клеточный , субклеточный и молекулярный уровень : клетки содержат внутриклеточные структуры, которые строятся из молекул .
• Организменный и органно-тканевой уровень : у многоклеточных организмов клетки составляют ткани и органы . Органы же, в свою очередь, взаимодействуют в рамках целого организма .
• Популяционный уровень : особи одного и того же вида, обитающие на части ареала, образуют популяцию .
• Видовой уровень : свободно скрещивающиеся друг с другом особи обладающие морфологическим, физиологическим, биохимическим сходством и занимающие определённый ареал (район распространения) формируют биологический вид .
• Биогеоценотический и биосферный уровень : на однородном участке земной поверхности складываются биогеоценозы , которые, в свою очередь, образуют биосферу .

Большинство биологических наук является дисциплинами с более узкой специализацией. Традиционно они группируются по типам исследуемых организмов: ботаника изучает растения , зоология — животных , микробиология — одноклеточные микроорганизмы . Области внутри биологии далее делятся либо по масштабам исследования, либо по применяемым методам: биохимия изучает химические основы жизни, молекулярная биология — сложные взаимодействия между биологическими молекулами, клеточная биология и цитология — основные строительные блоки многоклеточных организмов, клетки, гистология и анатомия — строение тканей и организма из отдельных органов и тканей, физиология — физические и химические функции органов и тканей, этология — поведение живых существ, экология — взаимозависимость различных организмов и их среды.

Передачу наследственной информации изучает генетика . Развитие организма в онтогенезе изучается биологией развития . Зарождение и историческое развитие живой природы — палеобиология и эволюционная биология .

На границах со смежными науками возникают: биомедицина , биофизика (изучение живых объектов физическими методами), биометрия и т. д. В связи с практическими потребностями человека возникают такие направления, как космическая биология , социобиология , физиология труда , бионика .

Искусственная жизнь — изучение жизни, живых систем и их эволюции при помощи созданных человеком моделей и устройств. Данная область науки изучает механизм процессов, присущих всем живым системам, невзирая на их природу. Хотя этот термин чаще всего применяется к компьютерному моделированию жизненных процессов, он также подходит и к жизни в пробирке ( англ. wet alife ), изучению искусственно созданных белков и других молекул.

Признаки жизни — характеристики, по которым можно обнаружить наличие жизни у организма, на местности, на других планетах.

Extraterrestrial life (alien life) is a hypothetical form of life that has arisen and exists outside the Earth. It is the subject of study of space biology and xenobiology, as well as one of the fictional objects in science fiction.

At present, science cannot give an unambiguous answer about the existence of life on Mars , however, the proximity and similarity to the Earth give prerequisites for the search for possible life forms . The question of the existence at present or in a past life on Mars remains open ^[24] .

Life after death or the afterlife is an idea of ​​the continuation of a person's conscious life after death . In most cases, such representations are due to the belief in the immortality of the soul , characteristic of various types of religious worldviews.

Representations of the afterlife are present in various religious and philosophical teachings. Among the main views:

• resurrection of the dead - people will be resurrected by God after death;
• reincarnation - the soul of a person returns to the material world in new incarnations;
• posthumous retribution - after death, the human soul goes to hell or paradise , depending on the earthly life of a person.

Immortality - life in physical or spiritual form that does not end indefinitely (or arbitrarily) for a long time.

Speaking of immortality in physical form, they distinguish between conditional biological immortality (the absence of individual death as the final stage of ontogenesis - see reproduction by division ) of unicellular organisms and the hypothetical biological immortality of complexly organized multicellular living beings ^[25] , including, and above all, human ^{[26] ]} .

Immortality in a spiritual form - in religious , philosophical , mystical and esoteric senses - means the eternal existence of an individual (" I ", soul , monad ), individual will ( palingenesis in the philosophical system of Arthur Schopenhauer ), the complex of components of an individual personality ( skandhi in the phenomenology of Buddhism ), a universal spiritual substrate (the transpersonal unconscious in the analytic psychology of Carl Gustav Jung , the noosphere in the religious and philosophical concept of Pierre Teilhard de Chardin , etc.).

A separate subject of religious and philosophical reasoning is immortality (eternity) as an attribute of God .

• Signs of life
• Teleonomy
• Homeostasis
• Human life
• Meaning of life
• Breeding
• Development
• Death
• Biology
• Biological evolution
• History of life on earth
• Origin of life
• Extraterrestrial life

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• Romanov S.F. 2010. Truths of the 21st Century (3rd edition), St. Petersburg, pp. 33–86. ( DOC version )
• Khaylov K. M. “Life” and “Life on Earth”: two scientific paradigms // Journal of General Biology: Journal. - 1998. - T. 59 , No. 2 . - S. 137-151 . - ISSN 0044-4596 .
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• Life // Big Soviet Encyclopedia : [in 30 vol.] / Ch. ed. A.M. Prokhorov . - 3rd ed. - M .: Soviet Encyclopedia, 1969-1978.
• What is life in terms of physics?
• Biology in questions and answers
• The problems of evolution .